Question

A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 km h and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:

Answer 1

Let the length of train be x km & its speed be y km/hr

Then, x/(y-2) = 9/(60*60)  

and x/(y-4) = 10/(60*60)

9y - 3600x = 18  

and 10y - 3600x = 40

y-400x = 2 and y - 360x = 4

Therefore  

40x = 2 or x = (2/40 *1000)m = 50 metres

Answer 2

Answer:

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2 kmph = ( 2 x 5 ( m/sec = 5 m/sec.

18 9

4 kmph = ( 4 x 5 ( m/sec = 10 m/sec.

18 9

• Let the length of the train be x metres and its speed by y m/sec.

Then, ( x ( = 9 and ( x ( = 10.

y - 5

9

y - 10

9

• Therefore 9y - 5 = x and 10(9y - 10) = 9x

=> 9y - x = 5 and 90y - 9x = 100.

On solving, we get: x = 50.